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Characterization of brake wear particle emissions from passenger cars: A case study of particle agglomeration and fragmentation.

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Title: Characterization of brake wear particle emissions from passenger cars: A case study of particle agglomeration and fragmentation.
Authors: Li, Jiachen1 (AUTHOR), Wang, Changyu1 (AUTHOR), Chen, Xiangxi1 (AUTHOR), Li, Aihong2 (AUTHOR), Ge, Yunshan1 (AUTHOR), Wang, Yachao1,3 (AUTHOR) wang_yachao@yeah.net
Source: Journal of Environmental Sciences (Elsevier). Dec2025, Vol. 158, p790-801. 12p.
Subject Terms: NANOPARTICLES, HIGH temperatures, URBAN pollution, SEPARATION (Technology), AUTOMOBILE emissions, AGGLOMERATION (Materials), PARTICULATE matter
Abstract: Brake wear particle (BWP) emissions are considered one of the dominant sources of particulate matter pollution in urban environments. BWP emissions have increased significantly under high-temperature conditions, emerging as a focal point of research interest. This study investigates the effect of brake temperatures on BWP emissions. The brake pad materials undergo violent decomposition and oxidation reactions and generate large amounts of incompletely oxidized organic products at temperatures above 475 °C. These organic products cause particles below 200 nm to proliferate, and nanoparticles below 40 nm account for the largest contribution of total BWPs. When the friction surface temperature exceeds 475 °C, the high-concentration BWPs below 200 nm will agglomerate into larger particles. High temperatures also cause the brake pad surface to delaminate and fragment into particles above 2.5 µm. In addition, when the initial brake speed is above 160 km/h, or the brake pressure is above 7 bar, there is a sharp increase in particles below 200 nm. The results suggest that a significant number of nanoparticles below 40 nm are inferred to be generated as the flash temperature of the friction surface reaches the violent reaction temperature. This study provides guidelines for designing low-emission brake pads, as improving the high-temperature resistance of brake pad material components possibly reduces BWP generation. [Display omitted] [ABSTRACT FROM AUTHOR]
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Database: Business Source Index
Description
Abstract:Brake wear particle (BWP) emissions are considered one of the dominant sources of particulate matter pollution in urban environments. BWP emissions have increased significantly under high-temperature conditions, emerging as a focal point of research interest. This study investigates the effect of brake temperatures on BWP emissions. The brake pad materials undergo violent decomposition and oxidation reactions and generate large amounts of incompletely oxidized organic products at temperatures above 475 °C. These organic products cause particles below 200 nm to proliferate, and nanoparticles below 40 nm account for the largest contribution of total BWPs. When the friction surface temperature exceeds 475 °C, the high-concentration BWPs below 200 nm will agglomerate into larger particles. High temperatures also cause the brake pad surface to delaminate and fragment into particles above 2.5 µm. In addition, when the initial brake speed is above 160 km/h, or the brake pressure is above 7 bar, there is a sharp increase in particles below 200 nm. The results suggest that a significant number of nanoparticles below 40 nm are inferred to be generated as the flash temperature of the friction surface reaches the violent reaction temperature. This study provides guidelines for designing low-emission brake pads, as improving the high-temperature resistance of brake pad material components possibly reduces BWP generation. [Display omitted] [ABSTRACT FROM AUTHOR]
ISSN:10010742
DOI:10.1016/j.jes.2025.02.024